1. Field of the Invention
The present invention relates to an anodizing method of a metal body using vibrationally, fluidly stirring and an apparatus for performing the same.
2. Description of the Related Art
In the field of manufacturing metal articles such as those made of aluminum, aluminum alloy, magnesium, magnesium alloy, etc. having an anodic oxide film on the surface of a metal body by using the anodizing process, it has been required to reduce the energy consumption and to improve the productivity and, in particular, to realize speeding up of the anodizing process, improvement in efficiency of oxide film forming. Furthermore, it has been required to realize the speeding up of the anodizing process under the condition that the higher temperature or room temperature treatment bath is used.
In fact, the most significant problem in the conventional anodizing process is that very long period of process time is necessary even if thinner oxide film having the thickness of 10 to 15 .mu.m is formed. Therefore, in the manufacturing line for the metal article, for example a sash window, made of anodized aluminum, the anodizing process must be performed with use of a plurality of treatment apparatuses arranged in parallel to each other in order to avoid stagnation of the line, because the anodizing process takes about 10 to 15 times of the duration of time as compared with the pre-treatment process and post-treatment process.
The inventor has proposed an anodizing process in which micro bubbles having a diameter of 50 to 80 .mu.m are continuously supplied to the treatment surface of alumimum body so that the anodizing rate is increased to the extent of 2 to 3 times of that of the conventional anodizing process. However, this process is still insufficient in the treatment rate and the treatment temperature.
On the other hand, in Japanese Patent Application Publication No. Sho-60-9600, there is disclosed an anodizing method in which numerous bubbles having a diameter of 0.001 to 4 mm are generated by the aeration apparatus in the electrolytic bath, and the bubbles are subjected to vibration of frequency of 10 to 200 Hz and allowed to move upwardly so that the efficiency of the anodizing process is improved. However, this technique is still insufficient, because oxygen generated by the electrolysis around the anode tends to form bubbles which is transferred to the atomosphere, and therefore the oxidative function thereof on the metal body becomes lowered. In addition, oxygen bubble formation results in increase of electrical resistance of the surface of the metal body and the higher voltage is required for the treatment so that the greater electric power is necessary and thus the heat release and energy loss become greater. Accordingly, it is considered that this conventional technique is practically used with the lower current density, for example 2 to 3 A/dm.sup.2, and therefore cannot realize the speeding up of the anodizing process under the condition that the higher temperature or room temperature treatment bath is used.